Body temperature (T-b) and metabolic rate (O-2 consumption) were measured c
ontinuously in naked mole-rats. Circadian rhythms were observed for both pa
rameters. Body temperature increased at the end of the light phase in a 12L
:12D cycle in three of four animals. The remaining animal exhibited a freer
unning rhythm of T-b When animals had access to running wheels, the time of
elevated T-b coincided closely with the time of increased running wheel ac
tivity. Rhythms of T-b continued following removal of the wheels, but the d
uration of increased T-b was decreased as compared to the duration of T-b e
levation in the presence of wheels. Metabolic rate was increased at the sam
e circadian phase as the increase in T-b and running wheel activity. These
observations extend our earlier findings on circadian rhythms of locomotor
activity in naked mole-rats and suggest that the circadian system may have
significant physiological functions in this subterranean rodent. (C) 2000 E
lsevier Science Inc. All rights reserved.